<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>css三角形制作</title>
    <style>
        .box1{
            width: 0;
            height: 0;

            border-top: 10px solid pink;
            border-bottom: 10px solid green;
            border-left: 10px solid blue;
            border-right: 10px solid yellow;
        }
    </style>
</head>
<body>
    <div class="box1">

    </div>
</body>
</html>